A virtual machine (VM) is a portion of software that, when executed on appropriate hardware, creates an environment allowing the virtualization of an actual physical computer system. Each VM may function as a self-contained platform, running its own operating system (OS) and software applications (processes). An OS is a set of programs that manages computer hardware resources and provides common services for application software. For hardware functions such as input and output and memory allocation, the OS typically acts as an intermediary between application programs and hardware. OSs may be found on a variety of devices, including desktop computers, servers, smartphones, video game consoles, and so forth.
A host machine (e.g., computer or server) is typically enabled to simultaneously run one or more VMs, where each VM may be used by a local or remote client. The host machine allocates a certain amount of the host's resources to each of the VMs. Each VM may use the allocated resources to execute applications, including an OS known as a guest OS or guest. The hypervisor virtualizes the underlying hardware of the host machine or emulates hardware devices, making the use of the VM transparent to the guest or the remote client using the VM. Typically, a hypervisor manages allocation and virtualization of computer resources and performs context switching, as may be necessary, to cycle between various VMs.
A host machine may be interconnected to an InfiniBand (IB) fabric. IB architecture developed by the Infiniband Trade Association (IB TA) defines a System Area Network (SAN) for interconnecting processor nodes and input/output (I/O) nodes through an IB fabric made of cascaded switches. Each IB node or switch may attach to a single or multiple switches or directly to another IB node or switch. An IB node connects to the fabric via a host channel adapter. Two or more IB subnets may be interconnected by one or more IB routers.
An IB endpoint may be identified by an IB service ID (SIDR). Alternatively, an IB endpoint may be identified by an internet protocol (IP) address and port number when, for example, using IP over IB. A port number may include a local identifier (LID) and a global identifier (GID). A LID is a 16-bit value that may be assigned when the corresponding port becomes active. A GID is a 128-bit value that may be formed by concatenating a 64-bit IB subnet prefix and a 64-bit GUID (Global Unique Identifier). Both the subnet prefix of the GID and LID may be assigned by a subnet manager, which is a component performing configuration and control of the subnet. IB architecture supports several methods of data transfer, also referred to as IB transports, including unreliable datagram, reliable datagram, reliable connected, and unreliable connected.